Pretty much all botnets target consumer devices and thus have ip addresses that are common for consumer devices. I'm not sure I buy that a mobile IP is worth more than a Comcast one, especially factoring in the available bandwidth.

That is certainly true. But in terms of scale even a claimed 5 million compromised android phones just barely registers while desktop botnets of six times that size are discovered.

The bandwidth constraints imposed by most users draconic data plans and the realities of limited battery life further put a fairly low cap on what a mobile botnet can do in this day and age. (both of which admittedly will hopefully change sooner rather than later...)